The iPhone 5S, stylized iPhone 5s, is a touchscreen-based smartphone developed by Apple Inc. It is part of the iPhone line, and was released on September 20, 2013. Apple held an event to formally introduce the phone (and its mid-range counterpart, the iPhone 5C) on September 10. Like the iPhone 4S, the 5S is a revised version of its predecessor, the iPhone 5, but also incorporates a 64-bit Apple A7 processor and a built-in fingerprint sensor called Touch ID on its updated home button.

The 5S ships with iOS 7, the seventh version of Apple's iOS mobile operating system, which is based on the concept of direct manipulation, using multi-touch gestures. Interface control elements consist of sliders, switches, and buttons. Interaction with the OS includes gestures such as swipe, tap, pinch, and reverse pinch, all of which have specific definitions in the context of the iOS operating system and its multi-touch interface. New features in iOS 7 include Control Center, AirDrop, iTunes Radio, and a new flat design directed by Jonathan Ive.

Reviews for the iPhone 5S were generally positive; some reviewers called it the best smartphone on the market. While Touch ID was praised as a major market changer, many commentators believed that iOS 7 was the most major update to the smartphone line. The 64-bit Apple A7 was also favored. Pundits claimed that it is a catalyst for various new applications from developers.